APHANIPTERA., 29 
fleas are, however, generally classified at the present day as the first 
sub-order of the Diptera, namely, the Diptera Aphaniptera, being thus 
placed between the Hemiptera Anoplura, or lice, and the Diptera 
Nemocera, Verrall, in his list of British Diptera (1888), places them 
in the Nemocera. 
Pulex irritans, L. (the Common Flea), 
This is the best-known of all the Pu/icide, and has been described 
over and over again. The following entomologists have given the 
best descriptions : Leach, Dugés, Bouché, Rosel, De Geer, Latreille, 
Newman, Kirby, and Westwood, and the works of these authors may 
be consulted for more detailed accounts. 
The abdomen large, inflated, reddish-brown, with two apical 
diverging bristles. Bristles developed on each segment, especially 
on the dorsal surface and around the genitalia. Head short and 
shining, minutely punctate. Antennz usually carried in the recep- 
tacles; basal part of maxilla thickened; palpi composed of four 
nearly equal joints. Mandible thickened and horny on one side, 
with smal! denticles ; thin and hyaline on the other, with numerous 
deep denticulations. 
Legs paler than the body. Coxz broad and flat, with a few 
scattered bristles on the upper surface. Femora also broad and flat, 
hairy ; a fringe of bristles on the inner side of the hind pair. Thick 
apical spines on the tibize and tarsi. Ungues fringed on the under 
surface by little spines (?). The first tarsal joints in the hind legs 
are the largest ; the fifth joints next in size ; the second, third, and 
fourth in decreasing succession. The two fore legs are differently 
constructed, two and five being the largest joints ; the first, third and 
fourth being nearly equal. The last tarsal joint always armed on the 
under surface by a few spines—generally four in the common flea. 
The Pygidium is composed of disc-like areolz, around which is a 
ring of rectangular rays. 
The male is armed with two stylets for copulation. The mode of 
copulation may easily be seen, by keeping a number of fleas in a glass 
test-tube. The coupling takes place tail to tail, the female (which 
is much larger than the male) stands over the male. The pairing 
sometimes only lasts a few seconds, but usually much longer. 
Leewenhoeck first discovered the spermatozoa of the flea) He 
described them as “serpent-like animalcules.” The flea may easily 
be dissected in water under the microscope, and the alimentary canal, 
testis, ovary, etc., easily seen. 
They are best mounted in balsam, after being well soaked in 
